1. Field of the Invention
This invention relates to a padlock having a shackle for interengagement with a device to be locked and in which the shackle is movable between locked and unlocked positions under the control of a key, and more particularly to a padlock of this type having a replaceable cylinder lock or key cylinder.
2. Description of the Prior Art
In key-operated shackle-type padlocks of the prior art, various arrangements have been provided to permit removing and interchanging the cylinder lock (sometimes referred to as the "key cylinder") in order to permit substituting cylinder locks having different tumbler pin combinations. The following United States patents show arrangements for interchanging cylinder locks or key cylinders in a shackle-type padlock:
U.S. Pat. No. 2,691,288 PA1 U.S. Pat. No. 3,835,675
Gary D. Childs PA2 Issued: Oct. 12, 1954 PA2 Guillermo W. Lippisch PA2 Issued: Sept. 17, 1974.
In providing a padlock construction which permits easy interchangeability of cylinder locks, it is important that the easy interchangeability be provided without sacrificing the lock's security, since the padlock should be so constructed as to be substantially tamperproof and substantially invulnerable to intruders.